Access denied renaming my user folder

I have been trying to follow this guide to rename my file system in Windows. Specifically my user folder in the Users folder. When I get to step 5 of the link I get 'Access Denied' despite opening the command prompt in administrator mode. I checked the permissions of the folder and I should have write access. I tried changing ownership of the folder to the Administrators group also and it still didn't work so I am unsure what's going on. I am using Windows 8.1 Pro for the record.

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